It has long been known in the art to utilize in a lathe or similar machine tool a spring collet which has a conically flared end that is longitudinally cut into three or more sections. Automatic collet closers are also well known. Typically, the collet closer includes a correspondingly shaped nosepiece which surrounds the collet, and a draw tube to axially draw the collet within the nosepiece, thus causing the collet to close upon a work piece that has been placed within it.
In general, and perhaps universally, the operation of an automatic collet closer has required a longitudinal or axial movement of the collet relative to the work piece.
My U.S. Pat. No. 3,361,433 issued Jan. 2, 1968 discloses an automatic collet closer which is operated hydraulically, by means of air pressure. This collet closer has been widely sold throughout the world for nearly twenty years. The headstock 10 of the machine lathe supports a rotatably driven hollow spindle 11 within which a hollow draw tube or draw bar 28 is positioned. The spindle 11 and draw bar 28 rotate in synchronism within the headstock 10, and a chuck 12 also rotates with them. Inside the chuck 12 are a hollow nosepiece 13a having a flared opening 14, and a spring collet 15 contained within the nosepiece. The collet closer, located rearwardly of the machine headstock, causes the draw bar 28 to move axially, and the spring collet 15 to move axially with the draw bar, so that the spring collet either closes upon a work piece B, or else opens to release the work piece, because of the interaction between the collet and the fixed nosepiece 13a.
In addition to my own collet closer referred to above, other collet closers have also been known and used, which operate to move a spring collet axially in order to close upon or release a work piece. Such other collet closers have also utilized a draw bar which is positioned inside a hollow spindle to rotate with the spindle, the draw bar being actuated in an axial direction to operate the collet.